Thomas j



- (No Model.)

T. J. BRAY.'

DRIVE SCREW. NO. 289,333i I Patented Nov. 27, 1883.

EHFLES SE5- watts "J. Bu -n, or ri;rrsn t?no, rExNsYL TANIA, ASSIGNOR t nno'rn'nas & PHILLIPS, or SAME PLACE. I

clear, and exact NITED} STAT PATENT TO oLivnn DRIVE-SCREW.

SPECIFICATION forming part of Letters Patent No. 289,333, dated November 27, 1863.

Application filed October 25, 1893. (X model.)

To all 11-h om, it may concern-.-

Be it known that I, Tnonas J. BRAY, of Pittsburg, in the county of Allegheny and State of Pennsylvania, have i uve'nted a new and useful I mp'rovemcnt in DriveScrews; and

I do hereby declare the following to be description thereof. Heretofore lag and drive screws have commonly been made with conical or eonoidal points of varying shapes and angles, and with V-threads, the base of the point being equal in diameter to the shank of the bolt. \Vhen such screws are driven into the wood, they tear and laccinte the fibers to a greater or less extent, according to the shape and size of the point.

\Vhen such screws are driven into a hole ofthe size ofthe shanka-t the bottom ofthethread, there is no guide by which an equal pressure or hearing can be insured all around the hole, and the consequence is that a bolt, when tints d ri ven, will not align properly and loses much of the holding power of the thread, while in suit spongywood it often fails to hold atall, and can be as easily withdrawn as a nail.

My improvement consists in making a lag, wood, or drive screw, having, a conical, tapering, or conoidal point, the base of which is of the same diameter as at the bottom ofthe thread, and with a cylindrical part between the base of the point and the connnencement; of the thread, to act as a guide or leading-point, in conjunction with a ratehet-thread, which will act as a wedge in still further separating the iibers withoutlacerating the same and weakening the hold of the screw.

To enable others skilled in the art to make and use my improvement, I will now describe it by referencclto' the accompanying drawings, in which- 1 i Figure 1 is a side elevation of my improved drive-screw. Fig. 2 is a viewofa portion of the drive-serew with a slightly-modified form of thread.

The screw has a head, a, shank b, a portion of which is ratchet-threaded, as at c and point d. In Fig. 1 there i. a cylindrical portion of thecore, showing between the turns of the thread, as at r.

a full,

part- 9 about equal to the shank of the bolt ,with the hole.

The diameter of the base of the point (2 is equal to the diameter of the cylindrical part or core e. Between the base. of the point and the commencement of the thread 0 is a e 'lindrical part, 1, which is of l the same diameter as the base of the point. This part 7 forms a guide or leading-point in driving the screw, causing it to align perfectly when driven into a previously-bored hole. Suchholes are usually made of a diameter equal to that of the core at the bottom of the threads. I prefer to make the length of the cylindrical 6o one-half the pitch ofthe thread, or slightly longer. Ido not, however, limit iuyselfto any particular length.-

Praetical experience has demonstrated that the laceration of the fibers of the wood,-which is consequent upon the useof dri.ve-screws, is due in a great measure to the point, and in a i measure to the V shape of the thread,and that when the point is equal, or nearly equal, in diameter to the diameter ofthe shank at the top of the threads, the wood will be much more seriously injured and lacerated than in the use of a leading-point, and especially if the thread has aratchet form, such as is shown in the drawings of this case. After the small point has passed into the wood and opened the tiber, the threads simply separate the fibers still farther without tearing them. This sepn aration causes the fibers which remain unbroken to be compressed" and to spring back over the base of the threads; hence, by the use of my improved screw I preserve the clasticity of the fibers to a much greater degree than where a large point is. used, and obtain a much better hold or grip in the wood. 85.

In using the screw with hardwoods, where a hole is previously bored for its reception, such holes should be made the size of the 017 lindrical part 9, which then becomes a guide, insuring the, perfec alignmentof the screw'go In Fig. 2 I show another form of ratchetthread, in which the inclined portion of one thread runs to the base of the nest succeeding thread. 5 Having thus dcscribad my iuyention, whatl claim, end desire to secure by Letters Patent, 1 substarltiallf as and for the purpess (1c is scribed, 0

A lag. wood, or drive screw h n'ing u rat'ehi In testimony whereof I hm'eheireunto set my (rt-thread and a tapering or colloidal point, .the 1' hand 'this 226 diwy of Oetoher, A. I). 1883.

I core of the screw 'at the bottom or the thread,

base of-which is of the same diameter as the THOMAS J. BRAY.

\Vitnesses': and a cylindrical part. between the base of the l \V. B'. CORWIN, 1 point and the commencement (3f the thread, i" T. B. KERR. 

